Novel device for notching and secondary battery manufactured using the same

ABSTRACT

Disclosed is a device for notching, at an interval of a unit electrode, a continuous electrode sheet in which an electrode active material is applied to one or both surfaces thereof, to form a plurality of unit electrodes from the electrode sheet, the device including a press to press notches on the top and the bottom of the electrode sheet at a set position, and a drawing member arranged at the rear of the press based on a feed direction of the electrode sheet, the drawing member drawing and transporting the electrode sheet by one pitch, a size corresponding to the unit electrode according to operation of the press, wherein, when one of the grippers draws and transports the electrode sheet, the remaining grippers move to a position for drawing.

TECHNICAL FIELD

The present invention relates to a novel device for notching. Specifically, the present invention relates to a device for notching, at an interval of a unit electrode, a continuous electrode sheet in which an electrode active material is applied to one or both surfaces thereof, to form a plurality of unit electrodes from the electrode sheet, the device comprising a press to repeatedly move backwards together with the electrode sheet according to the position of a continuously transferred electrode sheet and to return to the original position in the process of pressing notches on the top and bottom of the electrode sheet, and a drawing member arranged at the rear of the press based on a feed direction of the electrode sheet, the drawing member drawing and transporting the electrode sheet by one pitch, a size corresponding to the unit electrode according to operation of the press.

BACKGROUND ART

Recently, rechargeable secondary batteries are widely used as energy sources or auxiliary power devices of wireless mobile devices. In addition, secondary batteries are drawing great attraction as power sources of electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs) and the like suggested as alternatives to solve air pollution caused by conventional gasoline vehicles, diesel vehicles and the like using fossil fuels.

Such a secondary battery is manufactured in a state in which an electrode assembly is mounted in a battery case together with an electrolyte solution. Depending on manufacturing method, the electrode assembly is divided into a stack-type, a folding-type, a stack-folding type and the like. In the case of the stack type or stack-folding type electrode assembly, a unit assembly has a structure in which a cathode and an anode are laminated in this order such that a separator is interposed therebetween. In order to manufacture such an electrode assembly, manufacture of a cathode and an anode is first required.

That is, in order to manufacture a unit electrode such as a cathode and anode, first, a process for notching a continuous electrode sheet, in which an electrode active material is applied to one or both surfaces thereof, at an interval of a unit electrode, is required. The notching process is generally carried out by notching a part of the electrode sheet using a press.

The press apparatus is an apparatus for processing an electrode sheet, a material to be pressed, in the form of a predetermined shape and processing is generally carried out in a continuous feeding manner.

Such a continuous feeding manner is a method in which a press simultaneously transports and presses the electrode sheet, and is characterized in that the pressed electrode sheet is continuously fed without stop.

Describing this continuous feeding manner with reference to FIG. 1, the apparatus includes a press 20 to press an electrode sheet 10 in the form of a predetermined shape and a feeder 30 to feed the electrode sheet 10 to the press 20, and the press 20 also serves as a feeder. That is, the press 20 presses the electrode sheet 10 and, at the same time, transports half of a transport length, and the stand-by feeder 30 continuously transports the electrode sheet 10 in a state that the feeder 20 transports the remaining transport length. The electrode sheet 10 is continuously transported at a predetermined rate.

However, such a continuous feeding manner can feed the electrode sheet 10 at a predetermined rate, thus enabling stable pressing of the press 20, but, since it is difficult to feed the electrode sheet at a high rate due to inertia of a mold 22 that moves together with the press 10 when the press 10 moves left and right, a problem of deterioration in production efficiency occurs, thus resulting in increase in costs.

Accordingly, there is a need for development of a novel notching device to solve these problems.

DISCLOSURE Technical Problem

Therefore, the present invention has been made to solve the above problems and other technical problems that have yet to be resolved.

It is one object of the present invention to provide a notching device for stably forming notches on an electrode sheet at a high rate.

It is another object of the present invention to provide a secondary battery that exerts superior operational properties using the notching device.

Technical Solution

In accordance with one aspect of the present invention, provided is a device for notching, at an interval of a unit electrode, a continuous electrode sheet in which an electrode active material is applied to one or both surfaces thereof, to form a plurality of unit electrodes from the electrode sheet, the device including: a press to repeatedly move backwards together with the electrode sheet according to the position of continuously transferred electrode sheet and then return to the original position in the process of pressing notches on the top and the bottom of the electrode sheet; and a drawing member arranged at the rear of the press based on a feed direction of the electrode sheet, the drawing member drawing and transporting the electrode sheet by one pitch, a size corresponding to the unit electrode according to operation of the press.

That is, the notching device according to the present invention has a configuration in which the drawing member arranged at the rear of the press draws the electrode sheet by one pitch and the press only presses the electrode sheet transported by operation of the drawing member, thereby rapidly forming notches on the electrode, as compared to a conventional configuration in which a press also performs transport.

In a preferred embodiment, tension applied to the electrode sheet for transport of the electrode sheet may be supplied only from the drawing member in the process of pressing notches while the press moves backward.

Accordingly, the electrode sheet is transported only by the drawing member and the press does not transport the electrode sheet. Accordingly, the press can press high-quality notches on the electrode sheet.

In another embodiment, the drawing member may include two or more grippers to draw the electrode sheet by gripping or two or more rollers to draw the electrode sheet by rolling.

In a case where the drawing member is composed of two or more grippers, for example, when one of the grippers draws and transports the electrode sheet, the remaining grippers move to a position for drawing.

In another embodiment, the grippers comprise a first gripper adjacent to the press and a second gripper arranged at the rear of the first gripper to alternately draw the electrode sheet. Such a gripper including two grippers will also be broadly referred to as a “dual gripper”.

Specifically, operation of the dual gripper is as follows. While the first gripper draws the electrode sheet from the press and transports the same, the second gripper returns to the position for drawing and starts to transport the electrode sheet from the press immediately after transport of the first gripper is finished.

Meanwhile, the roller rotates at a predetermined rate, thereby drawing the electrode sheet at the predetermined rate by one pitch and feeding the same to the press.

The notches are formed on the top and the bottom of the electrode sheet, respectively, such that the notches are symmetrical to each other. For this reason, the notches can be easily cut during the subsequent cutting process.

Based on this configuration, a pressing rate of the press is for example 150 to 300 SPM (strokes per minute), which is increased, as compared to a conventional press also serving as a feeder. For example, the press serving as both a feeder and a presser has a pressing rate of 100 SPM or less.

The press may include a mold having at least two cavities to form a plurality of notches by one pressing operation. In this case, production efficiency can be improved.

Preferably, the mold has four to six cavities. The press including such a mold can form 4 to 6 notches through one pressing operation and the notch may have a shape such as a tap.

In some cases, the press may press notches between line units such that the electrode sheet is divided into two or more line units in a movement direction thereof and two or more unit electrodes are formed at respective line units at one pitch. In this case, the notch may be formed at the top and the bottom of the electrode sheet divided at respective lines and can improve production efficiency 2 fold, as compared to an electrode sheet not divided at line units.

In a preferred embodiment, the notching device may further include a tension portion to apply back tension to the electrode sheet at the rear of the press in a direction opposite to the transport direction of the drawing member.

The tension portion may include a roller set to be rotatable and a motor axially connected to the roller, wherein the motor synchronizes with the drawing member.

In this case, the motor stops operation at a point 5 to 10 mm in front of where the drawing member stops. As a result, the electrode sheet slips together with the roller and thus applies back tension to the electrode sheet.

The tension portion may include a roller to transport the electrode sheet, and a powder brake or a torque limiter to stop the roller.

Specifically, the powder brake or torque limiter stands the roller to apply back tension to the electrode sheet before the drawing member completes transport of the electrode sheet to the press.

The notching device may have a structure in which an unwinder winding the electrode sheet and a meandering controller to control meandering of the electrode sheet are arranged at the front of the tension portion in this order.

In this case, the device may further include a tension-maintaining module arranged between the meandering controller and the tension portion, to apply predetermined tension to the electrode sheet, together with the unwinder. Such a tension-maintaining module may be composed of either a weight dancer or an air dancer.

In some cases, the notching device may further include an inspector to inspect the electrode sheet notched by the press at the rear of the drawing member.

In this case, the inspector may include a camera to obtain an image data from the pressed electrode sheet and a decision module to analyze the image data. Meanwhile, the electrode sheet may include a tap. This tap may be formed together with the notch in the notching process.

The present invention also provides an electrode assembly manufactured using the notching device.

The electrode assembly has a structure in which a cathode and an anode are laminated in this order such that a separator is interposed therebetween.

For example, the cathode is produced by applying a slurry prepared by mixing a cathode mixture containing a cathode active material with a solvent such as NMP, to a cathode current collector, followed by drying and rolling.

The cathode mixture may further optionally contain a component such as a conductive material, a binder or a filler in addition to the cathode active material.

The cathode active material is, as a substance that causes electrochemical reactions, a lithium transition metal oxide comprising two or more transition metals and examples thereof include, but are not limited to, layered compounds such as lithium cobalt oxide (LiCoO₂) or lithium nickel oxide (LiNiO₂) substituted with one or more transition metals; lithium manganese oxide substituted with one or more transition metals; lithium nickel oxide represented by the formula of LiNi_(1-y)M_(y)O₂ (in which M=Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga, the lithium nickel oxide including one or more elements among the elements, 0.01≦y≦0.7); lithium nickel cobalt manganese composite oxides represented by Li_(1+z)Ni_(b)Mn_(c)Co_(1-(b+c+d))M_(d)O_((2-e))A_(e) such as Li_(1+z)Ni_(1/3)Co_(1/3)Mn_(1/3)O₂ or Li_(1+z)Ni_(0.4)Mn_(0.4)Cu_(0.2)O₂ (in which −0.5≦z≦0.5, 0.1≦b≦0.8, 0.1≦c≦0.8, 0≦d≦0.2, 0≦e≦0.2, b+c+d<1, M=Al, Mg, Cr, Ti, Si or Y, A=F, P or CO; and olivine lithium metal phosphate represented by the formula of Li_(1+x)M_(1-y)M′_(y)PO_(4-z)X_(z) (in which M=transition metal, preferably Fe, Mn, Co or Ni, M′=Al, Mg or Ti, X=F, S or N, −0.5≦x≦+0.5, 0≦y≦0.5, and 0≦z≦0.1).

-   -   The conductive material is commonly added in an amount of 1 to         30% by weight, based on the total weight of the mixture         comprising the cathode active material. Any conductive material         may be used without particular limitation so long as it has         suitable conductivity without causing adverse chemical changes         in the battery. Examples of conductive materials include         conductive materials, including graphite; carbon blacks such as         carbon black, acetylene black, Ketjen black, channel black,         furnace black, lamp black and thermal black; conductive fibers         such as carbon fibers and metallic fibers; metallic powders such         as carbon fluoride powders, aluminum powders and nickel powders;         conductive whiskers such as zinc oxide and potassium titanate;         conductive metal oxides such as titanium oxide; and         polyphenylene derivatives.

The binder is a component which enhances binding of an electrode active material to a conductive material and current collector. The binder is commonly added in an amount of 1 to 30% by weight, based on the total weight of the mixture comprising the cathode active material. Examples of the binder include polyvinylidene, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubbers, fluororubbers and various copolymers.

The filler is a component optionally used to inhibit expansion of the electrode. Any filler may be used without particular limitation so long as it does not cause adverse chemical changes in the manufactured battery and is a fibrous material. Examples of the filler include olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers.

The cathode current collector is generally manufactured to have a thickness of 3 to 500 μm. Any cathode current collector may be used without particular limitation so long as it has suitable conductivity without causing adverse chemical changes in the manufactured battery. Examples of the cathode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, and aluminum or stainless steel surface-treated with carbon, nickel, titanium or silver. These current collectors include fine irregularities on the surface thereof so as to enhance adhesion to electrode active materials. In addition, the current collectors may be used in various forms including films, sheets, foils, nets, porous structures, foams and non-woven fabrics.

For example, the anode is produced by applying a slurry prepared by mixing an anode mixture containing an anode active material with a solvent such as NMP to an anode current collector, followed by drying. The anode mixture may further optionally contain a component such as a conductive material, a binder or a filler as mentioned above.

Examples of the anode active material include carbon and graphite materials such as natural graphite, artificial graphite, expanded graphite, carbon fiber, hard carbon, carbon black, carbon nanotubes, perylene, activated carbon; metals alloyable with lithium, such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt and Ti and compounds containing these elements; composites of carbon and graphite materials with a metal and a compound thereof; and lithium-containing nitrides. Of these, a carbon-based active material, a silicon-based active material, a tin-based active material, or a silicon-carbon-based active material is more preferred. The material may be used alone or in combination of two or more thereof.

The anode current collector is generally fabricated to have a thickness of 3 to 500 μm. Any anode current collector may be used without particular limitation so long as it has suitable conductivity without causing adverse chemical changes in the battery. Examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, and copper or stainless steel surface-treated with carbon, nickel, titanium or silver, and aluminum-cadmium alloys. Similar to the cathode current collectors, the anode current collectors include fine irregularities on the surface thereof so as to enhance adhesion to electrode active materials. In addition, the current collectors may be used in various forms including films, sheets, foils, nets, porous structures, foams and non-woven fabrics.

The separator is interposed between the cathode and the anode. As the separator, an insulating thin film having high ion permeability and mechanical strength is used. The separator typically has a pore diameter of 0.01 to 10 μm and a thickness of 5 to 300 μm. As the separator, sheets or non-woven fabrics made of an olefin polymer such as polypropylene and/or glass fibers or polyethylene, which have chemical resistance and hydrophobicity, are used. When a solid electrolyte such as a polymer is employed as the electrolyte, the solid electrolyte may also serve as both a separator and an electrolyte.

The present invention also provides a secondary battery having a structure in which the electrode assembly is sealed together with the lithium salt-containing non-aqueous electrolyte in a battery case.

The lithium salt-containing, non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt and examples of preferred electrolytes include non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes and the like.

Examples of the non-aqueous solvent include non-protic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate and ethyl propionate.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohols, polyvinylidene fluoride, and polymers containing ionic dissociation groups.

Examples of the inorganic solid electrolyte include nitrides, halides and sulfates of lithium such as Li₃N, LiI, Li₅NI₂, Li₃N—LiI—LiOH, LiSiO₄, LiSiO₄—LiI—LiOH, Li₂SiS₃, Li₄SiO₄, Li₄SiO₄—LiI—LiOH and Li₃PO₄—Li₂S—SiS₂.

The lithium salt is a material that is readily soluble in the above-mentioned non-aqueous electrolyte and examples thereof include LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imides.

Additionally, in order to improve charge/discharge characteristics and flame retardancy, for example, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride or the like may be added to the non-aqueous electrolyte. If necessary, in order to impart incombustibility, the non-aqueous electrolyte may further contain halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride. Further, in order to improve high-temperature storage characteristics, the non-aqueous electrolyte may further contain carbon dioxide gas or the like.

The battery case may be a cylindrical can, a rectangular can or a pouch to which a lamination sheet is thermally bonded. Of these, the pouch-shaped case may be generally used due to advantages such as low weight, low manufacturing cost and easy shape change.

The laminate sheet includes an inner resin layer in which thermal bonding is performed, a barrier metal layer, and an outer resin layer that exerts durability.

The outer resin layer should have superior resistance to exterior environments, thus requiring a predetermined level or more of tensile strength and weather resistance. In this regard, a polymer resin for the outer coating layer may contain polyethylene naphthalate (PEN), polyethylene terephthalate (PET) or oriented nylon that exhibit superior tensile strength and weather resistance.

In addition, the outer coating layer is made of polyethylene naphthalate (PEN) and/or is provided at the outer surface thereof with a polyethylene terephthalate (PET) layer.

Polyethylene naphthalate (PEN) exhibits superior tensile strength and weather resistance even at a small thickness as compared to polyethylene terephthalate (PET) and is thus suitable for use as an outer coating layer.

The polymer resin for the inner resin layer may be a polymer resin that has a thermal bonding property (thermal adhesion property), low hygroscopicity of the electrolyte solution to prevent permeation of the electrolyte solution thereinto and is neither expanded nor deposited by the electrolyte solution and is more preferably a chlorinated polypropylene (CPP) film.

In a preferred embodiment, the laminate sheet according to the present invention may include an outer coating layer having a thickness of 5 to 40 μm, a barrier layer having a thickness of 20 to 150 μm, and an inner sealant layer having a thickness of 10 to 50 μm. When the thicknesses of respective layers of the laminate sheet are excessively small, barrier performance of the materials and improvement in strength cannot be expected and, on the other hand, when the thicknesses are excessively large, disadvantageously, processability is deteriorated and thicknesses of sheets are increased.

Such a secondary battery may be used for a battery cell used as a power source of small devices as well as a unit battery for middle and large battery modules including a plurality of battery cells used as power sources of middle and large devices requiring high-temperature stability, long cycle characteristics, high rate characteristics and the like.

Examples of preferred middle and large devices include, but are not limited to, power tools powered by battery-driven motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bikes (E-bikes), electric scooters (E-scooter); electric golf carts; electric power storage system and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partial schematic view illustrating a conventional notching device;

FIG. 2 is a partial schematic view illustrating a notching device according to one embodiment of the present invention;

FIG. 3 is a plane schematic view illustrating the electrode sheet of FIG. 2;

FIG. 4 is a plane schematic view illustrating an electrode sheet according to another embodiment of the present invention;

FIG. 5 is a plane schematic view illustrating a notching device according to another embodiment of the present invention;

FIG. 6 is a schematic view illustrating a configuration of the notching device according to another embodiment of the present invention;

FIG. 7 is a schematic view illustrating a process of the notching device according to another embodiment of the present invention;

FIG. 8 is a graph showing a rate of the notching device of FIG. 1; and

FIG. 9 is a graph showing a rate of the notching device of FIG. 2.

BEST MODE

Now, the present invention will be described in more detail with reference to the following examples. These examples are provided only for illustrating the present invention and should not be construed as limiting the scope and spirit of the present invention.

FIG. 2 is a partial schematic view of a notching device according to one embodiment of the present invention. FIG. 3 is a plane schematic view of the electrode sheet of FIG. 2.

Referring to these drawings, a notching device 100 a includes a press 20 a and a drawing member 30 to notch, at an interval of an unit electrode 16, a continuous electrode sheet 10 in which an electrode active material is applied to both surfaces thereof, to manufacture a plurality of unit electrodes 16 from the continuous electrode sheet 10.

The press 20 a repeats moving backwards together with the electrode sheet 10 according to the position of continuously transferred electrode sheet 10 and then returning to the original position in the process of pressing notches 11 and 12 on the top and the bottom of the electrode sheet 10, respectively.

The drawing member 30 is arranged at the rear of the press 20 a based on a feed direction of the electrode sheet 10, and draws and transports the electrode sheet 10 by one pitch, a size corresponding to the unit electrode according to operation of the press 20 a.

In addition, tension applied to the electrode sheet 10 for transport of the electrode sheet 10 is supplied only from the drawing member 30 in the process of pressing notches 11 and 12 while the press moves backward.

In addition, the drawing member 30 includes a first gripper 30 b and a second gripper 30 c of a dual gripper structure that draw the electrode sheet 10 by gripping, the first gripper 30 b is adjacent to the press 20 a and the second gripper 30 c is arranged at the rear of the first gripper 30 b.

That is, the first gripper 30 b and the second gripper 30 c are arranged at the rear side of the press 20 a based on the feed direction of the electrode sheet 10, and when the first gripper 30 b draws and transports the electrode sheet 10, the second gripper 30 c moves to the position for drawing.

Specifically, while the first gripper 30 b draws the electrode sheet 10 from the press 20 a and transports the same to a position of B, the second gripper 30 c returns to a position of C for drawing and starts to transport the electrode sheet 10 from the press 20 a consecutively from the position of B at which transport of the first gripper 30 b is completed.

The notches 11 and 12 are formed by the press 20 a on the top and the bottom of the electrode sheet 10 such that they are symmetrical to each other.

In addition, the press 20 a includes a mold 22 a, thus pressing the electrode sheet 10 to form notches 11 and 12, and synchronizes with the first gripper 30 b and the second gripper 30 c.

The first gripper 30 b and the second gripper 30 c feed the electrode sheet 10 to the press by one pitch (p) by a drawing operation in a state of gripping the electrode sheet 10. The first gripper 30 b and the second gripper 30 c alternately operate. That is, while the first gripper 30 b operates, moves from the position ‘A’ to the position ‘B’ and feeds the electrode sheet 10 by one pitch, the second gripper 30 c returns from the position ‘D’ to the position ‘C’ (stand-by position) and is arranged so that it feeds the electrode sheet 10 successively (immediately) from the first gripper 30 b.

When the operation of first gripper 30 b is finished, that is, when the first gripper 30 b moves to the position ‘B’, completes feeding and the press 20 a presses the notches, the second gripper 30 c grips the electrode sheet 10 to prepare for feeding and, the second gripper 30 c moves from the position ‘C’ to the position ‘D’ and successively feeds the electrode sheet 10 immediately after pressing via the press 20 a is finished.

Such a configuration in which two grippers 30 b and 30 c are used prevents intermittent feeding from occurring, as occurs when one gripper is used, while the gripper feeds the electrode sheet 10 and then returns to the original position, and thus further improves production efficiency.

FIG. 4 is a plane schematic view illustrating an electrode sheet according to another embodiment of the present invention.

Referring to FIG. 4 together with FIG. 2, the press 20 a presses notches 13 and 14 between a first line and a second line, and two unit electrodes are divided into two line units at one pitch (p) in a movement direction of the electrode sheet 10 a and two unit electrodes are notched at respective line units in one pitch (p).

The press 20 a includes a mold 22 b having four pairs of cavities to form four taps 15 and notches 11, 12, 13 and 14 through a single pressing operation.

In addition, the press 20 a forms four taps 15 in the process of forming the notches 11, 12, 13 and 14 on the electrode sheet 10 a. These taps 15 are formed in a region of the electrode sheet 10 a to which an electrode active material is not applied and have a symmetrical structure at respective unit lines of the electrode sheet 10 a.

FIG. 5 is a schematic view illustrating a configuration of the notching device according to another embodiment of the present invention.

The notching device of FIG. 5 is the same as the notching device of FIG. 2 except that the drawing member includes a roller 30 d that rotates at a predetermined rate and a detailed description thereof is thus omitted.

FIG. 6 is a schematic view illustrating a configuration of the notching device according to another embodiment of the present invention. FIG. 7 is a schematic view illustrating a process of the notching device of FIG. 6.

Referring to these drawings together with FIGS. 2 and 3, a notching device 200 includes an unwinder 50, a meandering controller 60, a tension portion 70, a press 20 a that presses notches 11 and 12 on the top and the bottom of an electrode sheet 10, a drawing member 30 to draw the electrode sheet 10 and transport the same to the press 20 a, an inspector 80 and a rewinder 90.

The tension portion 70 includes a tension-maintaining module 71 that applies back tension to the electrode sheet 10 at the front of the press 20 a in a direction opposite to the transport direction of the drawing member 30 and applies predetermined tension of the electrode sheet 10.

In addition, the meandering controller 60 that controls meandering of the electrode sheet 10 is arranged between the unwinder 50 that winds the electrode sheet 10 and the tension portion 70 that applies back tension to the electrode sheet 10, and an inspector 80 that inspects the electrode sheet 10 on which the notches 11 and 12 are pressed is arranged at the rear of the drawing member 30.

The rewinder 90 to rewind the inspected electrode sheet is arranged at the rear of the inspector 80, and the inspector 80 includes a camera 81 to obtain an image data from the notch-pressed electrode sheet and a decision module 82 to analyze the image data.

Specifically, the electrode sheet 10 to be pressed is wound on the roller of the unwinder 50, the roll of the unwinder 50 is axially connected to a servo motor, and the electrode sheet 10 is thus actively unwound depending on a control signal applied to the servo motor.

The meandering controller 60 prevents the electrode sheet 10 from meandering in the process of transporting the electrode sheet. A sensor (not shown) constituting the meandering controller 60 senses meandering of the electrode sheet 10 in the process of transporting the electrode sheet 10, thereby causing the first roll 61 and the second roll 62 constituting the meandering controller 60 to move in an axial direction and prevents the electrode sheet 10 from meandering. The electrode sheet 10 that is subjected to meandering control while passing through the meandering controller 60 is transported to the tension portion 70.

The tension portion 70 controls tension of the electrode sheet 10 at the front of the press 20 a and thereby prevents the electrode sheet 10 from meandering, and the electrode sheet 10 that passes through the tension portion 70 is transported to the press 20 a through an idler roller 72.

The press 20 a presses a notch on the electrode sheet 10 according to the mold at a set position. Such an electrode sheet 10 is fed to the press 20 a by a distance (p) between the notches 12 according to the operation of the drawing member 30 and the distance is referred to as a “pitch (p)”.

The drawing member 30 draws the electrode sheet 10 and transports the same to the press 20 a by one pitch according to the pressing rate of the press 20 a.

The inspector 80 confirms whether pressing of the press 20 a is within an acceptable error range through visual testing. The electrode sheet 10 passing through the inspector 80 is transported to the rewinder 90 and is wound on the roll 91.

If necessary, another tension portion (not shown) may be arranged between the inspector 80 and the rewinder 90 so that the tension portion 70 maintains the tension of the electrode sheet 10 at the rear of the press 20 a and thereby enables the electrode sheet 10 to maintain a tight state.

In addition to these components, an apparatus to supply a protective material wound together with the pressed electrode sheet 10 may be added in order to protect the pressed electrode sheet 10 when the pressed electrode sheet 10 is wound on the roll of the rewinder 90.

In addition, the electrode sheet 10 is transported to the tension portion 70 in a state that meandering of the electrode sheet 10 is controlled by the meandering controller 60.

The press 20 a presses the electrode sheet 10 at a set position, and the drawing member 30 draws the electrode sheet 10 at a high rate when pressing of the press 20 a is finished, and feeds the electrode sheet 10 to the press 20 a again. Accordingly, the electrode sheet 10 jitters due to inertia since it rapidly moves and stops. This problem is solved by the tension portion 70.

The tension portion 70 includes a tension-maintaining module 71 and back tension module (not shown), and the tension-maintaining module 71 applies predetermined tension to the electrode sheet 10 transported to the press at the front of the press. A weight dancer serving as the tension-maintaining module 71 is axially connected to a pneumatic cylinder (not shown) and includes a potential meter (not shown) to measure a movement angle of the weight dancer.

The movement of the weight dancer 71 is measured by the potential meter and the unwinder 50 unwinds the material to a large or small extent (to a certain degree), based on the measured value and thereby maintains tension applied to the electrode sheet 10. More specifically, when the weight dancer 71 moves in a counterclockwise direction, the unwinder 50 increases a rotation rate of the servo motor, unwinds more material from the roll, and the weight dancer 71 is returned back by the force of the pneumatic cylinder and applies tension to the electrode sheet 10.

When the weight dancer 71 moves in a clockwise direction, the unwinder 50 reduces a rate of rotation of the servo motor and thereby unwinds less material and the weight dancer 71 returns to the original position and reduces tension applied to the electrode sheet 10.

As such, the weight dancer 71 synchronizes with the unwinder 50 and maintains predetermined tension of the electrode sheet 10 transported to the press 20 a.

The back tension module (not shown) prevents meandering of the electrode sheet 10 caused by instantaneous operation of the drawing member 30 and the second gripper 30 c. This back tension module is arranged at the front of the press 20 a and preferably includes a servo roller.

The servo roller is axially connected to the servo motor (not shown) and controls rotation of the servo roller using a control signal.

Such a servo roller is set such that it moves synchronously with the drawing member 30. That is, when the drawing member 30 operates, the servo motor rotates the servo roller in a forward direction, and when the operations of the drawing member 3 is finished, the servo motor stops and the servo roller stops rotation. Preferably, the servo motor stops at a point 5 to 10 mm in front of where the drawing member 30 stops and thereby prevents the servo roller from rotating by inertia after the drawing member 30 stops. As such, before the drawing member 30 stops operation, that is, before transport of the electrode sheet 10 to the press 20 a is finished, the serve motors stop rotation of the servo roller and prevent further drawing of the electrode sheet 10 using friction generated by slip between the electrode sheet 10 and the servo roller. As a result, the electrode sheet 10 is further drawn by the drawing member 30 and jittering of the electrode sheet 10 caused by inertia can thus be solved.

The camera 81 may have any configuration so long as the configuration enables digital image data to be obtained, and preferably includes a camera using a charge-coupled device (CCD) with excellent image quality as an image sensor, and a decision module 82 decides whether or not pressing of the electrode sheet 10 is good according to an algorithm.

The electrode sheet 10 subjected to a pitch test in the inspector 80 is fed to the rewinder 90 through the rollers and the pressed electrode sheet is wound on the rewinder 90.

Meanwhile, a rear tension portion including a weight dancer and an air dancer to maintain tension of materials may further be present between the inspector 80 and the rewinder 90.

In addition, the meandering controller may further be present between the inspector 80 and the rewinder 90. In this case, the meandering controller prevents the electrode sheet 10 from meandering when the pressed material is wound on the roll again.

FIG. 8 is a graph showing a rate of the notching device of FIG. 1. FIG. 9 is a graph showing a rate of the notching device of FIG. 2.

Referring to these drawings together with FIGS. 1 and 2, in the notching device 100 a of FIG. 2, a transport time of the electrode sheet per cycle is T, which is decreased to about ⅓ of t of the notching device 100 of FIG. 1. This indicates that the notching device 100 a of FIG. 2 notches the electrode sheet 3-times faster than the notching device 100 of FIG. 1.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

As apparent from the afore-going, the notching device according to the present invention stably forms notches on an electrode sheet at a high rate and thereby greatly improves production efficiency of the nothing process. 

1. A device for notching, at an interval of a unit electrode, a continuous electrode sheet in which an electrode active material is applied to one or both surfaces thereof, to form a plurality of unit electrodes from the electrode sheet, the device comprising: a press to repeatedly move backwards together with the electrode sheet according to the position of the continuously transferred electrode sheet and then return to the original position in the process of pressing notches on the top and the bottom of the electrode sheet; and a drawing member arranged at the rear of the press based on a feed direction of the electrode sheet, the drawing member drawing and transporting the electrode sheet by one pitch, a size corresponding to the unit electrode according to operation of the press.
 2. The device according to claim 1, wherein tension applied to the electrode sheet for transport of the electrode sheet is supplied only from the drawing member in the process of pressing notches while the press moves backwards.
 3. The device according to claim 1, wherein the drawing member comprises two or more grippers to draw the electrode sheet by gripping or two or more rollers to draw the electrode sheet by rolling.
 4. The device according to claim 3, wherein, when one of the grippers draws and transports the electrode sheet, the remaining grippers move to a position for drawing.
 5. The device according to claim 4, wherein the grippers comprise a first gripper adjacent to the press and a second gripper arranged at the rear of the first gripper to alternately draw the electrode sheet.
 6. The device according to claim 5, wherein, while the first gripper draws the electrode sheet from the press and transports the same, the second gripper returns to the position for drawing and starts to transport the electrode sheet from the press immediately after transport of the first gripper is finished.
 7. The device according to claim 3, wherein the roller rotates at a predetermined rate.
 8. The device according to claim 1, wherein the notches are formed on the top and the bottom of the electrode sheet, respectively, such that the notches are symmetrical to each other.
 9. The device according to claim 1, wherein the press comprises a mold having at least two cavities to form a plurality of notches through one pressing operation.
 10. The device according to claim 1, wherein the press presses notches between line units such that the electrode sheet is divided into two or more line units in a movement direction thereof and two or more unit electrodes are formed at respective line units at one pitch.
 11. The device according to claim 1, further comprising a tension portion to apply back tension to the electrode sheet at the rear of the press in a direction opposite to the transport direction of the gripper.
 12. The device according to claim 11, wherein the tension portion comprises a roller set to be rotatable and a motor axially connected to the roller, wherein the motor synchronizes with the drawing member.
 13. The device according to claim 11, wherein an unwinder winding the electrode sheet and a meandering controller to control meandering of the electrode sheet are arranged at the front of the tension portion in this order.
 14. The device according to claim 1, wherein the electrode sheet comprises a tap.
 15. An electrode assembly manufactured using the notching device according to claim
 1. 16. A secondary battery in which the electrode assembly according to claim 15 is sealed in a battery case together with an electrolyte solution.
 17. A battery pack comprising two or more of the secondary batteries according to claim 16 as a unit battery.
 18. The battery pack according to claim 17, wherein the battery pack is used as a power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) or an electric power storage system. 